The inventive concepts disclosed herein relate to a low noise optical amplifier for low light detection, and to optical systems employing such a low noise optical amplifier.
Low light level imaging is important for applications ranging from photography to night vision. One example application is in helmet mounted displays, such that may be deployed on a helmet for a pilot operating an aircraft. Other applications include astronomical imaging. Low light levels may occur, for example, for night time imaging under overcast conditions.
Light detection systems include imaging devices that may employ focal plane array (FPA) detectors. Typically, an FPA will have very many pixels, each pixel appropriate for separately detecting a plurality of impinging photons. Light detectors and FPAs, however, eventually are unable to operate in ultra-low light conditions.
In low light level imaging conditions, only a few photons per pixel may arrive each frame-time. In this case, the imaging quality in an optical imaging system may be very grainy or noisy, which can render images taken at night unusable. Dark current and digital readout circuitry create noise that exceeds the minimal signal created by the few photons. In the lowest light level conditions, so few photons may arrive that no image is captured at all.